Original equipment manufacturers (“OEMs”) of automobile sound systems typically include sound equalization (“EQ”) in a radio head unit that is installed in a new automobile. The radio head unit is typically logically situated between an audio source and an audio system that may include an amplifier and speakers.
The equalization is typically designed to improve a listener's audio experience inside the car, usually when OEM audio equipment, such as a speaker, is in use, but often causes degraded sound quality when the OEM audio equipment is replaced by aftermarket audio equipment.
Original equipment manufacturers may provide a transfer function to a microprocessor that is logically situated between the digital audio source and the transducers or speakers. The transfer function may “improve” the acoustic signal, for example, to compensate for shortcomings in OEM audio equipment, by operating on a digital audio data packet to digitally enhance the acoustic signal in the cabin. The transfer function may act by applying weights to different frequencies in the acoustic spectrum.
If a component of the vehicle's sound system, or a component of the vehicle itself, is changed after installation of the transfer function, the weights may no longer improve the listener experience.